-
+
Functions and Operators
string NOT SIMILAR TO pattern ESCAPE escape-character
- The SIMILAR TO operator returns true or
- false depending on whether its pattern matches the given string.
- It is much like LIKE, except that it
- interprets the pattern using the SQL standard's definition of a
- regular expression. SQL regular expressions are a curious cross
- between LIKE notation and common regular
- expression notation.
-
+ The SIMILAR TO operator returns true or
+ false depending on whether its pattern matches the given string.
+ It is much like LIKE, except that it
+ interprets the pattern using the SQL standard's definition of a
+ regular expression. SQL regular expressions are a curious cross
+ between LIKE notation and common regular
+ expression notation.
+
- Like LIKE, the SIMILAR TO
- operator succeeds only if its pattern matches the entire string;
- this is unlike common regular expression practice, wherein the pattern
- can match any part of the string.
- Also like
- LIKE, SIMILAR TO uses
- _> and %> as wildcard characters denoting
- any single character and any string, respectively (these are
- comparable to .> and .*> in POSIX regular
- expressions).
-
+ Like LIKE, the SIMILAR TO
+ operator succeeds only if its pattern matches the entire string;
+ this is unlike common regular expression practice, wherein the pattern
+ can match any part of the string.
+ Also like
+ LIKE, SIMILAR TO uses
+ _> and %> as wildcard characters denoting
+ any single character and any string, respectively (these are
+ comparable to .> and .*> in POSIX regular
+ expressions).
+
- In addition to these facilities borrowed from LIKE,
- SIMILAR TO supports these pattern-matching
- metacharacters borrowed from POSIX regular expressions:
+ In addition to these facilities borrowed from LIKE,
+ SIMILAR TO supports these pattern-matching
+ metacharacters borrowed from POSIX regular expressions:
-
-
- | denotes alternation (either of two alternatives).
-
-
-
- * denotes repetition of the previous item zero
- or more times.
-
-
-
- + denotes repetition of the previous item one
- or more times.
-
-
-
- Parentheses () can be used to group items into
- a single logical item.
-
-
-
- A bracket expression [...] specifies a character
- class, just as in POSIX regular expressions.
-
-
-
+
+
+ | denotes alternation (either of two alternatives).
+
+
+
+ * denotes repetition of the previous item zero
+ or more times.
+
+
+
+ + denotes repetition of the previous item one
+ or more times.
+
+
+
+ Parentheses () can be used to group items into
+ a single logical item.
+
+
+
+ A bracket expression [...] specifies a character
+ class, just as in POSIX regular expressions.
+
+
+
- Notice that bounded repetition (?> and {...}>)
- are not provided, though they exist in POSIX. Also, the dot (.>)
- is not a metacharacter.
-
+ Notice that bounded repetition (?> and {...}>)
+ are not provided, though they exist in POSIX. Also, the dot (.>)
+ is not a metacharacter.
+
- As with LIKE>, a backslash disables the special meaning
- of any of these metacharacters; or a different escape character can
- be specified with ESCAPE>.
-
+ As with LIKE>, a backslash disables the special meaning
+ of any of these metacharacters; or a different escape character can
+ be specified with ESCAPE>.
+
Some examples:
- The substring> function with three parameters,
- substring(string from
- pattern for
- escape-character), provides
- extraction of a substring that matches an SQL
- regular expression pattern. As with SIMILAR TO>, the
- specified pattern must match to the entire data string, else the
- function fails and returns null. To indicate the part of the
- pattern that should be returned on success, the pattern must contain
- two occurrences of the escape character followed by a double quote
- (">). The text matching the portion of the pattern
- between these markers is returned.
-
+ The substring> function with three parameters,
+ substring(string from
+ pattern for
+ escape-character), provides
+ extraction of a substring that matches an SQL
+ regular expression pattern. As with SIMILAR TO>, the
+ specified pattern must match to the entire data string, else the
+ function fails and returns null. To indicate the part of the
+ pattern that should be returned on success, the pattern must contain
+ two occurrences of the escape character followed by a double quote
+ (">). The text matching the portion of the pattern
+ between these markers is returned.
+
Some examples:
- zone="functions-info">
+
current
- zone="functions-info">
+
current
- zone="functions-info">
+
current
- zone="functions-info">
+
- zone="functions-info">
+
- zone="functions-info">
+
- zone="functions-info">
+
Unix-domain socket.
- zone="functions-info">
+
- zone="functions-info">
+
tables from a catalog display.)
- zone="functions-info">
+
server started.
- zone="functions-info">
+
- zone="functions-info">
+
- zone="functions-info">
+
- zone="functions-info">
+
- zone="functions-info">
+
- zone="functions-info">
+
- zone="functions-info">
+
- zone="functions-info">
+
- zone="functions-info">
+
- zone="functions-info">
+
- zone="functions-info">
+
- zone="functions-info">
+
- zone="functions-info">
+
- zone="functions-info">
+
this way — if the name can be recognized at all, it must be visible.
- zone="functions-info">
+
- zone="functions-info">
+
- zone="functions-info">
+
- zone="functions-info">
+
- zone="functions-info">
+
- zone="functions-info">
+
- zone="functions-info">
+
- zone="functions-info">
+
- zone="functions-info">
+
- zone="functions-info">
+
pg_class> catalogs.
- zone="functions-info">
+
- zone="functions-info">
+
- zone="functions-info">
+
- zone="functions-info">
+
about database objects
- zone="functions-admin">
+
- zone="functions-admin">
+
- zone="functions-admin">
+
of the server
functions
- zone="functions-admin">
+
- zone="functions-admin">
+
- zone="functions-admin">
+
- zone="functions-admin">
+
backend processes
subprocess.
- zone="functions-admin">
+
- zone="functions-admin">
+
- zone="functions-admin">
+
- zone="functions-admin">
+
- zone="functions-admin">
+
pg_current_xlog_insert_location
- zone="functions-admin">
+
- zone="functions-admin">
+
- zone="functions-admin">
+
the actual disk space usage of database objects.
- zone="functions-admin">
+
- zone="functions-admin">
+
- zone="functions-admin">
+
- zone="functions-admin">
+
- zone="functions-admin">
+
- zone="functions-admin">
+
- zone="functions-admin">
+
..>>.
- zone="functions-admin">
+
is negative, it is relative to the end of the file.
- zone="functions-admin">
+
- zone="functions-admin">
+
released for other sessions' use.
- zone="functions-admin">
+
Only would-be exclusive lockers are locked out.
- zone="functions-admin">
+
acquired now.
- zone="functions-admin">
+
pg_try_advisory_lock_shared
shared rather than exclusive lock.
- zone="functions-admin">
+
and in addition, an SQL warning will be raised by the server.
- zone="functions-admin">
+
pg_advisory_unlock_shared
except to release a shared advisory lock.
- zone="functions-admin">
+